In recent years, an ultrasonic sensor is widely used for detecting objects, and the ultrasonic sensor having an ultrasonic transducer is proposed in, for example, Japanese patent document No. JP-A-2004-159351. The sensor disclosed in the above reference includes an ultrasonic transducer having a piezoelectric element pasted on a bottom of a cylindrical housing of the transducer and a case for housing the transducer that is inserted from an opening formed thereof. The piezoelectric element is electrically coupled with a circuit board in the case by a lead.
The lead for coupling the piezoelectric element with the circuit board is replaced with a connection pin, mainly due to an increasing demand for improvement of workability. Therefore, an alternative structure for electrically coupling the piezoelectric element with the circuit board by using a connection pin with an insulating base disposed on the bottom of the housing with the connection pin piercing therethrough is proposed, for example, in Japanese patent documents No. JP-A-H08-130795, and No. JP-A-H11-87491.
The ultrasonic transducer is conventionally disposed on a case with a vibration absorbing material pasted thereon for preventing the vibration to be transmitted to the case when the ultrasonic wave is generated by the transducer. That is, an outer surface of the transducer and a bottom of it are covered by the vibration absorbing material for preventing the vibration to be transmitted to an opening of the case.
However, the elasticity of the absorbing material may lead to a deformation of the absorbing material, and thereby causing a break of the connection pin due to, for example, a dislocation of the transducer in an insertion direction into the case by a pressing force from outside. That is, the electrical coupling between the connection pin and the circuit board is broken due to the pressing force for warping the connection pin in the insertion direction for causing a reaction force at a soldered portion of the connection pin.
Particularly, when an additional foaming member is disposed under the base of the housing, the pressing force on the transducer causes a larger dislocation of the transducer, and the problem described above may become more distinctive.